1. Field of the Invention
The invention relates to a display device, and particularly relates to a display device including a resistive element on a substrate including pixels.
2. Background Art
For instance, an active-matrix liquid crystal display device is configured to sequentially select each pixel row in respective pixels formed in a matrix state in a substrate by turning on thin-film transistors formed on respective pixels by a scanning signal to be supplied through a common gate signal line and to supply a video signal to respective pixels of the pixel row at the selected timing through a drain signal line connected in common to pixels corresponding to other pixel rows.
The thin-film transistors of respective pixels have a configuration which is very much liable to receive electrostatic damage, therefore, it is known that an electrostatic protection circuit is formed on the substrate in the vicinity of a liquid crystal display area formed as an aggregate of pixels.
For example, it is known that the electrostatic protection circuit is formed between an output terminal of a drive circuit for driving the respective pixels and a signal line formed in the liquid crystal display area and a large current pulse due to electrostatic discharge generated at the output terminal is reduced by a resistive element in the electrostatic protection circuit (refer to Patent Document 1 below).
The above electrostatic protection circuit is usually formed in parallel with the formation of pixels for reducing manufacturing processes.
Patent Document 1: JP-A-6-51346
Patent Document 2: JP-A-2005-303119
When the display device including the above configuration is manufactured, there is a case that a so-called resist reflow process is applied (refer to the above Patent Document 2).
When a thin-film transistor of each pixel is formed, a photoresist film used as a mask when forming a drain electrode and a source electrode by patterning is allowed to remain as it is, and a semiconductor layer positioned at a layer under the drain electrode and the source electrode is etched by using a deformed photoresist film obtained by allowing the photoresist film to reflow as a mask, which makes an additional mask process when the semiconductor layer is selectively etched unnecessary.
The resist reflow process is applied also when the electrostatic protection circuit is manufactured, and the formation of the resistive element is also performed in parallel with the manufacture of the thin-film transistor.
However, in the case that the resistive element is formed by applying the resist reflow process in which the semiconductor layer is used as a resistive material and the same material as the drain electrode and the source electrode of the thin-film transistor is used for respective terminals, the inconvenience occurs that it is difficult to form the semiconductor layer long enough in the direction the current flows. That is, it is difficult to secure the length of the semiconductor layer for sufficiently forming a desired resistance value.
In the case that the photoresist film used as a mask when forming respective terminals by patterning is allowed to reflow, the deformed photoresist film on one terminal side and the deformed photoresist film on the other terminal side obtained by the reflow are not continuously formed on the semiconductor layer, therefore, there occurs a cut (separated) point in the semiconductor layer between respective terminals when the semiconductor layer is etched by using the deformed photoresist film as a mask in the above state.